What's all this MP3, .wav, etc?
Sound can be stored as a digital file on a computer in a number of different formats. Common ones that you might encounter are .mp3, .wma (compressed formats) and .wav, .aif (not compressed).
Sound can be 'compressed' so that it takes up less space ('wav' files are not compressed, 'mp3' files are). There are different amounts of compression which can be used, and greater compression means that while a file takes up less space, the quality of the sound falls. When these files are played back, the playing machine needs to be able to read the compressed sound, and it is the ability to do this in future, as well as the compromised quality of the sound, which is an issue for archivists.